public class digui{
	public int C(int n,int m) throws sumException{
	if(n<m||n<=0||m<=0){
	throw new sumException(n,m);
	}
	else{
	if(m==1)
	return n;
	else if(n==m)
	return 1;
	else
	return C(n-1,m-1)+C(n-1,m);
	}
	}
}